LIGHTROOM: Develop module tools don't produce changes in my image

When I use the quick develop tools in the Library module of Lightroom 5.3, the selected image reflects the changes, but when I use the tools in the develop module, the image doesn't change. Nothing works. When I click the crop tool, half the time the image completely disappears. I have uninstalled LR 5.3 and re-installed it from CC. Same problem. Why is this happening?